In a process for manufacturing a semiconductor device, rear-surface polishing is performed to remove an unnecessary film (burr) formed at an outer circumferential part of the rear surface of a semiconductor wafer. The polished state of the rear surface of a semiconductor wafer, for example, can be determined based on a change in the rotational torque of a stage on which the semiconductor wafer is mounted. However, according to such a technique, while the polished state of the rear surface can be roughly acquired in a macroscopic manner, it is difficult to perform a high-precision determination.